Near-death experiences (NDE) have been long reported across time and cultures. An astounding 5 to 10 percent of the general population is estimated to have memories of an NDE, including somewhere between 10 and 23 percent of heart attack survivors. A growing number of scholars now accept NDEs as a unique mental state that can offer novel insights into the nature of consciousness. Neuroscientists no longer question anymore the reality of near-death experience: People who report an experience really did experience something.

Those who undergo an NDE also return with a quality from the experience, which very often changes their life.

A handful of researchers, mostly emergency room doctors, began collecting qualitative data about NDEs after the 1975 publication of psychiatrist and physician Raymond A. Moody’s book Life after Life, which detailed patients’ accounts of near-death experiences. Since then, only a few research teams have attempted to empirically investigate the neurobiology of NDEs. But their findings are already challenging long-held beliefs about the dying brain, including that consciousness ceases almost immediately after the heart stops beating. This discovery has important implications for current resuscitation practices. If we understand the mechanisms of death, then this could lead to new ways of saving lives.

Like psychedelic drugs and other means of altering consciousness, NDEs could also serve as probes for revealing fundamental truths about the mind and brain. Such states are disturbances to the system of consciousness and when you disturb a system, you understand better how it works. If we want to understand the nature of experience, we have to take into account what’s happening at the margins of nonordinary states.

Moreover, there are important existential implications, although exactly what those might be continues to be debated in the scientific literature and at conferences, including at a 2023 meeting held by the New York Academy of Sciences. It explored consciousness through the lens of death, psychedelics and mysticism. Since these transcendent experiences are found in the major world religions and traditions scientists are curious as to if they have some greater purpose for helping humanity cultivate understanding and awareness of consciousness. The weightiness of threse sort of questions makes careful study of NDEs and their rigorous interpretation all the more critical, in order to disentangle empirical findings from beliefs.

Many people who had an NDE describe one or more of a specific set of characteristics. They may recall separating from their body and viewing it in real time from above. They may pass through tunnels and see light, encounter deceased relatives or compassionate entities, and have a sense of vastness and deep insight. People may undergo a life review and morally evaluate the choices they have made, including by experiencing the joy or pain their actions caused others. What’s intriguing is that when people die, they don’t evaluate themselves based on their own standards of morals, they evaluate themselves based on a universal standard.

Although most people describe their NDE in glowing terms, a minority recount visits to hell-like regions, encounters with demonic beings or terrifying voids. In a 2019 study, Charlotte Martial, a neuroscientist at the University of Liège in Belgium and her colleagues found that among 123 people who reported an NDE, 14 percent classified it as negative—a proportion Martial says she’s “sure” is an underestimate because of how disturbing these memories can be.

Somewhat surprisingly, religious people don’t seem to be more inclined toward NDEs. There is, however, preliminary evidence of another group being more likely to have NDEs: those who are prone to REM sleep intrusion, a condition that occurs when rapid eye movement (REM) sleep intrudes into wakefulness and blends elements of dreaming and waking. During the seconds or minutes it lasts for, people may have an out-of-body experience, sense that someone or something is in the room with them, or want to move but find that they can’t. In 2019 Daniel Kondziella, a neurologist at the Copenhagen University Hospital and his colleagues recruited a sample of 1,034 adults from the general population in 35 countries. Ten percent of the study participants had experienced an NDE, and of those, 47 percent also reported REM sleep intrusion—a statistically significant association. Among the people who had not had NDEs, just 14 percent reported REM sleep intrusion.

Still, little is known about the neurobiology of NDEs. Open questions include whether they are driven by a single, core mechanism or are a more variable response to understanding somehow that death is near. A few researchers, including Martial, are peering into the brains of people who are approaching or undergoing death, in the hope of understanding what is going on.

In 2023 Jimo Borjigin of the University of Michigan Medical School and her colleagues published what they suspect could be a signature of NDEs in the dying brain. The researchers analysed EEG data from four comatose patients before and after their ventilators were removed. As their brains became deprived of oxygen, two of the dying patients exhibited a paradoxical surge of gamma activity, a type of high-frequency brain wave linked to the formation of memory and the integration of information.

Borjigin had seen the same upwelling of activity in previous studies of the brains of healthy rats during induced cardiac arrest. In the rodents, the surge occurred across the entire brain. In humans, though, it was confined primarily to the junction of the brain’s temporal, parietal and occipital lobes, a region involved in multiple features of consciousness, including visual, auditory and motion processing. Past research has also associated the region with out-of-body sensations, as well as with altruism and empathy. Although these are all regular components of NDEs, Borjigin says, it’s impossible to know whether the two patients actually experienced an NDE because they did not live to tell about it.

A 2023 study led by Sam Parnia, director of critical care and resuscitation research at the N.Y.U. Grossman School of Medicine and detailed in his forthcoming 2024 book, Lucid Dying, provides further evidence of brain activity after patients’ hearts have stopped. Parnia and his colleagues worked with 25 hospitals in the U.S., the U.K. and Bulgaria to review EEG and brain-oxygen data from 567 people who experienced an in-hospital cardiac arrest. Medical staff managed to collect interpretable EEG data from 53 of these patients. Most showed an electrical flatline during the crisis, but in around 40 percent of those cases, neurological activity consistent with that of conscious brains transiently reemerged—in some instances up to an hour into CPR.

A different subset of 53 patients from the study survived. Doctors collected EEG and brain-oxygen levels for too few of these people to draw a correlation between any potential memory they had of the event and their brain activity. The authors were able to interview 28 of the survivors, and six had a NDE.

Parnia and his colleagues also sought to test conscious and unconscious awareness, including reports of out-of-body experiences, by projecting a series of 10 random images on a tablet placed near patients’ heads and by playing a repeated recording of the names of three fruits—apple, pear, banana—to them through headphones every minute for five minutes while they were unconscious. None of the survivors could remember the images that had been projected. One person who had a recalled experience of death correctly named the fruits in order, although this could have been by chance, Parnia says.

According to Parnia, this study presents a coherent, mechanistic explanation for how and why people have recalled experiences of death. When someone starts dying, Parnia says, the brain becomes dysfunctional. Some actions are immediately lost, such as brain stem reflexes, but others that are normally suppressed to optimise performance for ordinary life suddenly become disinhibited because the brain’s natural braking systems are no longer working. As a result, your entire consciousness comes to the fore. The purpose of this change, he suggests, is to prepare the person “for a new reality”—the transition from life to death, a condition in which, Parnia believes, consciousness endures.

Other scientists flatly disagree. Kondziella suggests that when you have an NDE, you must have a functioning brain to store the memory. And you have to survive with an intact brain so you can retrieve that memory and be able to tell about it. A functioningg brain is necessary for that, so “all those arguments that NDEs prove that there’s consciousness outside the brain are simply nonsense”.

Kondziella, Martial, and others instead theorise that NDEs might be part of a last-ditch survival tactic. Species across the animal kingdom “play dead”—a behaviour technically called thanatosis—when they perceive a mortal threat, typically from an attacking predator. If fight-or-flight fails, the instinct to feign death kicks in as an attempt to forestall the danger. The animal becomes immobilised and unresponsive to external stimuli—but with continued awareness so that, given a chance, it can escape. Kondziella believes the evolutionary aspect really is the key to understanding what NDEs are and how they came about. For him there is a perfectly valid biological explanation.

In their latest study, Martial and her colleagues plan to use the most rigorous approach to date to collect both subjective and objective data from around 100 patients, including EEG and brain-oxygen readings, plus information from several rounds of interviews and surveys with survivors in the group. The University of Liège team is also trying to more thoroughly evaluate claims about out-of-body experiences. Around 79 percent of people who have an NDE report leaving their body, and some wake up knowing facts about their environment that they seemingly should not know. That’s something she wants to test objectively.

To this end, she and her colleagues have decorated the hospital resuscitation room with unexpected objects and images, some of which are hidden in places that could be viewed only from the vantage point of someone near the ceiling. While a patient is in the resuscitation room, including while they are conscious, the team plays an audio clip of various words and animal sounds once every minute. They will test for recollections of any images or sounds in follow-ups with surviving participants, and they will also use video recordings to compare people’s memories with reality.

An easier approach to studying NDEs is via safe proxies such as hypnosis, induced fainting and psychedelic drugs. None of these methods produce true NDEs, but the states they trigger may have some overlap with the dying brain. In 2018 Timmermann, Martial and their colleagues published a study comparing NDEs with the effects of N,N-dimethyltryptamine (DMT), a mind-altering component of ayahuasca, a South American plant-derived psychedelic brew. Trace amounts of DMT also occur endogenously in humans. There’s speculation that that’s somehow underlying NDEs.

In the study, 13 volunteers received intravenous DMT in a lab setting and rated their experience on a scale commonly used to measure NDEs, developed by psychiatrist Bruce Greyson in 1983. The researchers compared the DMT group’s scores and subjective accounts with other people’s taken from an NDE database that Martial and her colleagues have been compiling since 2016. (The database includes around 2,000 accounts, accepted from anyone who contacts the Liège team claiming to have had an NDE and then fills out a lengthy questionnaire.)

They found “striking overlap” between the DMT and NDE groups with people in both describing a sense of entering into an unearthly realm, separating from their body, encountering mystical beings and seeing a bright light. People in both groups also reported feelings of peace, unity and joy. There was just one significant difference: those in the NDE group more frequently experienced reaching a border demarcating a point of no return.

Roland Griffiths, a psychiatrist at Johns Hopkins University who pioneered studies of psilocybin and who died last October, reported similar findings with his colleagues in 2022. The authors compared 3,192 people who had undergone an NDE, a psychedelic drug trip or a non-drug-induced mystical experience. The team found remarkably similar long-term outcomes across subjects in all three groups, including a reduced fear of death and lasting positive effects of insights they had gained.

In another study currently undergoing peerreview, Martial, Timmermann and their colleagues interviewed 31 people who had experienced an NDE and had also tried a psychedelic drug—LSD, psilocybin, ayahuasca, DMT or mescaline—to see what they had to say about the similarities and differences between the events. Participants reported stronger sensory effects during their NDE, including the sensation of being disembodied, but stronger visual imagery during their drug trip. They reported feelings of spirituality, connectedness and deeper meaning across both.

In comparisons of these mystical experiences, Bossis has found that the common ground is in things like a profound, deep sense of love—that all is love and that consciousness is love. He studies the effects of psilocybin in people with terminal cancer, focusing on relieving end-of-life distress, enhancing spirituality, and providing a greater sense of meaning and fulfillment in life. There’s also a sense of transcending time and a greater acceptance of the mystery of life and death.

Regardless of how people interpret NDEs, studying them may provide a better understanding of mind and brain, and hopefully further illuminate some of the deepest mysteries of existence.

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